Classifying patients In relation to their clinical conditions and complexity of care needs, three profiles of patients with SBI have been identified: the critically patient, the complex patient and the frail patient. The critically ill patient is a patient with abnormal vital parameters who requires constant monitoring and may need immediate therapeutic interventions. The complex patient is an individual with significant comorbidities who requires complicated, expensive and often invasive diagnostic investigations and/or numerous therapies sometimes conflicting with each other with a strong risk of interactions. The complexity of care increases in "frail patients". Frail patients have: (i) a marked susceptibility to develop acute illnesses that are manifested by atypical clinical pictures;(ii) rapid fluctuations of health, even in the same day, with a strong tendency to develop complications (failure cascade); (iii) a high risk of adverse events and iatrogenic events; (iv) slow and, almost always, only partial recovery; (v) continued requirements for medical interventions, need for ongoing assistance; and (vi) a high risk of mortality.